CVE-2025-9467 Overview
CVE-2025-9467 is an input validation weakness in the Vaadin framework's Upload component. When developers use the Upload component's start listener to validate metadata about incoming uploads, an authenticated attacker can bypass that validation and submit uploads that should have been rejected.
The issue affects multiple long-term support branches of Vaadin, including versions 7, 8, 14, 23, and 24. The flaw is tracked under CWE-20: Improper Input Validation and is documented in the Vaadin Security Advisory CVE-2025-9467.
Critical Impact
Attackers with low privileges can bypass upload validation checks implemented in the start listener, leading to unauthorized file uploads that could impact integrity and availability of the target application.
Affected Products
- com.vaadin:vaadin-server versions 7.0.0 through 7.7.47 and 8.0.0 through 8.28.1
- com.vaadin:vaadin versions 14.0.0 through 14.13.0, 23.0.0 through 23.6.1, and 24.0.0 through 24.7.6
- com.vaadin:vaadin-upload-flow versions 2.0.0 through 14.13.0, 23.0.0 through 23.6.1, and 24.0.0 through 24.7.6
Discovery Timeline
- 2025-09-04 - CVE-2025-9467 published to NVD
- 2026-09-14 - Last updated in NVD database
Technical Details for CVE-2025-9467
Vulnerability Analysis
The Vaadin Upload component exposes a start listener that fires when an upload begins. Developers commonly attach validation logic to this listener to inspect metadata such as file name, content type, and declared size before allowing the transfer to proceed.
Under normal operation, rejecting the upload from within the start listener should terminate the request. In vulnerable versions, that rejection is not consistently enforced by the server-side handler. An attacker can craft an upload request that continues transmitting file content even after the listener signals rejection.
The result is that any security control implemented solely in the start listener can be bypassed. Applications that rely on this mechanism to block dangerous file types, oversized files, or restricted metadata are exposed to unauthorized uploads.
Root Cause
The root cause is improper input validation ([CWE-20]) in the Upload component's server-side request handling. The framework fails to fully honor the rejection state produced by the start listener before consuming the incoming file stream.
Attack Vector
Exploitation requires network access to a Vaadin application that uses the Upload component with start-listener-based validation. The attacker must have low-level privileges sufficient to reach the upload endpoint. No user interaction is required. See the Vaadin Security Advisory CVE-2025-9467 for reference details.
No public proof-of-concept exploit is currently available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.
Detection Methods for CVE-2025-9467
Indicators of Compromise
- Application logs showing successful uploads whose metadata (file name, MIME type, size) matches values that server-side start-listener logic should have rejected.
- Upload requests where the HTTP body continues to transmit file content after the application has logged a validation failure event.
- Presence of files in upload storage locations that violate documented business rules on file type or size.
Detection Strategies
- Review Vaadin dependency versions across all deployed applications and flag any build using vaadin-server, vaadin, or vaadin-upload-flow in the vulnerable ranges listed in the advisory.
- Add server-side auditing that compares start-listener validation decisions against the final state of stored uploads, so mismatches surface as security events.
- Correlate web server access logs with application logs to identify upload sessions that completed despite validation rejection.
Monitoring Recommendations
- Ingest application and web server logs into a centralized analytics platform and alert on discrepancies between rejected upload events and files written to disk.
- Monitor upload endpoints for unusual file types, unexpected content sizes, or high volumes of upload attempts from a single authenticated principal.
- Track dependency inventories using software composition analysis to detect regressions to vulnerable Vaadin versions after remediation.
How to Mitigate CVE-2025-9467
Immediate Actions Required
- Inventory all applications that include Vaadin dependencies and identify any using the Upload component with a start listener for validation.
- Upgrade affected artifacts to the fixed versions published by Vaadin as soon as change management permits.
- Move critical validation logic out of the start listener alone and add server-side checks that run after upload completion until patching is verified.
Patch Information
Vaadin has released fixed versions for each supported branch. Upgrade to 7.7.48, 8.28.2, 14.13.1, 23.6.2, or 24.7.7 or newer, depending on the branch in use. Vaadin versions 10-13 and 15-22 are no longer supported; migrate those deployments to the latest 14, 23, or 24 release. Refer to the Vaadin Security Advisory CVE-2025-9467 for the complete artifact and version matrix.
Workarounds
- Implement supplemental validation in a succeededListener or finishedListener that inspects the completed upload and deletes files that violate policy.
- Enforce upload restrictions at an upstream layer such as a web application firewall or reverse proxy that inspects Content-Type and Content-Length headers.
- Restrict access to upload endpoints using role-based access control so only trusted authenticated users can invoke them until patches are deployed.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
